Induction of dormancy in aphid parasitoids: implications for enhancing their field effectiveness

Abstract

The aphid parasitoid Pauesia unilachni Gahan entered diapause even under short night conditions at 20°C in oviparae of Schizolachnus pineti F. on Pinus sylvestris L., but Praon volucre Hal. did not under the same conditions in oviparae of Acyrthosiphon pisum Harris. Praon volucre or Aphidius matricariae Hal. reared in anholocyclic strains of Aulacorthum solani Kalt., Aphis gossypii Glover and Myzus ascalonius Doncaster did not enter diapause under long night conditions at 15°C. A cold shock could induce hibernal quiescence and diapause of Praon volucre in Acyrthosiphon pisum, but only hibernal quiescence occurred in this parasitoid developing in anholocyclic hosts. These observations show that environmental cues (temperature and photoperiod) as well as internal factors via host aphid such as host aphid life cycle, aphid morph and host plant quality are involved in the induction of dormant stages in aphid parasitoids. The importance of these findings is discussed in terms of enhancing parasitoid activity in the field.